Frances Dinkelspiel grew up with the vague knowledge that her great-great-grandfather had something to do with Wells Fargo Bank. But she didn't learn how crucial Isaias Hellman had been to the growth of California - its banking, oil, transportation and wine industries, its universities and synagogues - until she began rummaging through his files at the California Historical Society eight years ago.

"What I discovered was a great untold story," says Dinkelspiel, who tells that tale in her rich new book, "Towers of Gold: How One Jewish Immigrant Named Isaias Hellman Created California." The subtitle sounds a bit hyperbolic until you read about the extraordinary achievements of the man who came to the dusty little pueblo of Los Angeles in 1859 at age 16 with nothing but dreams. A smart, conservative and hardworking gent, he made a fortune and became the Golden State's greatest financier in the late 19th and early 20th centuries.

"I see Hellman as the man behind the curtain on some level," says Dinkelspiel, a former San Jose Mercury News reporter and freelance writer who turns 49 today. "If you look at almost any major deal during his lifetime, Hellman is somewhere in the background. I think the ultimate benefit of this research is that I've been able to show that there was this financial mastermind who was able to steer things in certain directions and make deals that helped develop California." Hellman, she adds, not only played a major role in building Los Angeles and San Francisco - he developed trolley systems in both cities, funded oil exploration in Southern California and helped rebuild San Francisco after the 1906 quake and fire - he was a prime mover in bridging north and south.

Dinkelspiel, a fifth-generation Californian who grew up in San Francisco and studied history at Stanford - her grandfather, Lloyd Dinkelspiel, was president of the university board of trustees and the auditorium there is named for her grandmother - writes perceptively about the Hellmans' German Jewish background and how it shaped their behavior and outlook.

Hellman, whose great-grandson is San Francisco financier, philanthropist and banjo player Warren Hellman, "grew up in Bavaria when Jews were not accorded full citizenship and were not allowed to work and live where they wanted," Dinkelspiel says. "There had been frustrations built up for centuries. And I think when Hellman came to the United States this frustration was released. It was not only true for Hellman but also for the Haas family and the Walter family (another prominent San Francisco family). For the first time in their lives, these men had the opportunity to do whatever they wanted. I think Hellman took that very seriously. He wanted to create and give back."

Anti-Semitism, of course, was always there - in 1873, the Los Angeles Star alluded to Shylock in an editorial attacking Hellman's growing influence - and he was acutely aware of how he was perceived.

From the beginning, Hellman allied himself with Yankees and Californios, bringing both Jews and gentiles onto the board of the Nevada Bank when he took over the San Francisco institution in 1890 (it merged with Wells Fargo Bank in 1904) and forming a wide circle of friends. "I think the Jews who came here were trying to adapt to American life," says Dinkelspiel. "They weren't trying to hide. They were trying to sort of partner their religious traditions with the entrepreneurial spirit of California."

Dinkelspiel, who lives in Berkeley with her husband and two teenage daughters, thinks her great-great-grandfather would be distressed by the current financial crisis and the way banks made such risky loans. "Hellman always insisted on decent collateral or he wouldn't loan," she says. "He was willing to say no to making a buck if it didn't make sense."